1. Field of the Invention
The present invention relates to a travel route indicating device for use in a vehicle, and more particularly to an improved apparatus for determining and visually indicating a current location, a travelling path and a current travel direction of an automotive vehicle to its driver.
2. Description of the Prior Art
In the attempt to prevent the driver of an automotive vehicle or the like from losing his way when driving such as at night or in unfamiliar surroundings away from his desired route of travel, there have been developed a variety of apparatus which are designed to visually indicate continuously or discretely a due current position or the like information on the vehicle by way of an indication panel or display screen including a related road map or the like disposed at the driver's seat so that he may be provided with a necessary ready guidance relating to the vehicle's current status of travelling with respect to a desired course of travel.
In the conventional travel route indicating apparatus for such an application, a current travel distance of a vehicle is detected in accordance with its speed of travel and time by using a distance detecting section, a current bearing and a current quantity of azimuthal deviation of the vehicle are detected by a bearing detecting section which employs a gas rate sensor or the like adapted to detect a possible angular velocity produced about the axis of yawing motion of the vehicle, a current location of the vehicle along its travel route is obtained from an arithmetic operation on the thus-obtained data, and the results of this arithmetic operation are stored in sequence, and indicated visually by way of spot information varying from time to time on a display screen upon which there is presented a transparent road map of routes or roads along which the vehicle is to travel.
With the conventional construction as described above, it is common in practice that because of the advantageous performance of such a device known as a gas rate sensor which exhibits a substantial resistance to physical vibrations, a substantial sensitivity and a rapid responsiveness when compared with a mechanical detecting device such as a gyroscope or the like. the gas rate sensor is a typical means enployed to detect an azimuthal motion of the vehicle, which is designed to detect an angular velocity produced from a turning motion of the vehicle in terms of a fractional or fine amount of difference in the sensed heat factor as generated by a possible change in the gas flow within the gas rate sensor from an azimuthal deviation such as generated in the turning motion of the vehicle. However, it is to be noted that it is essential for the gas rate sensor to have a constant internal temperature for attaining an accurate bearing detection of an object upon which it is mounted, and that its internal temperature does not rise up to a desired constant level until a substantial period of time has passed after starting thereof. At the same time, according to such temperature characteristic of the gas rate sensor, it is susceptible to a possible change in the external temperature therearound as an immediate disturbance factor. In this respect, it is undesirable to employ this gas rate sensor for such an application, without any particular condiserations for temperature control.
In this connection, there has been made available no desirable installation of such gas rate sensor having a high sensitivity, and due to the difficulty in handling for use in an automotive vehicle, installation work has been uneconomical in practice.
The present invention is essentially directed toward overcoming such inconveniences and difficulties as experienced in the conventional design of a visual travel route inicating apparatus which incorporates a gas rate sensor.